Depression is one of the most common neurologic diseases around the world, mainly caused from low levels of the neurotransmitters, especially serotonin (5-HT). Increased 5-HT levels, which are antidepressant, can be obtained by administration of tryptophan* amino acid (a precursor to 5-HT).
Nigella sativa** is an herb with a history of use for centuries in the Middle East, North Africa, and Asia. It can be used for many diseases and as a tonic to promote general good health. The present study was designed to learn more about the antidepressant effects of Nigella sativa in rats.
Nigella oil was given to half of the rats by mouth for 4 weeks. Then, a Forced Swim Test (FST) was performed to evaluate the antidepressant effects. The rats were placed in a glass tank of water too deep for them to stand in. They were forced to swim, to try to climb out, and/or struggle to stay afloat. Those who struggled for a shorter time before giving up were considered more depressed, and those who struggled longest were considered to be the least depressed. The animals were retrieved and put in their cages.
After the FST, the animal’s brains were tested for 5-HT levels. These levels were compared to the animals rating on the FST. The results showed that repeated administration of black seed oil had an antidepressant effect. The rats which received the nigella treatment struggled longer before they gave up on the FST and had higher levels of tryptophan in the blood and brain than did those which were not given nigella. The rats which did not receive treatment struggled for shorter periods of time.
CONCLUSION: Long term treatment with Nigella sativa oil may be a useful treatment to prevent stress and depression in humans.
*Tryptophan and 5-hydroxytryptophan may be taken as supplements to produce serotonin in the nervous system.
**Nigella sativa (nigella) is also known as black seed and as black cumin.
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